PROBABLE ROLE OF CALCIUM COMPOUNDS IN INCREASING CROP YIELDS ON DEEP-PLOWED SOLONETZ SOIL

Abstract

Samples of Ap horizon and Ap–Bnt horizon mixtures of four Solonetz soils were treated with NH₄NO₃, CaSO₄, and CaCO₃ singly and in combinations. Calcium carbonate increased the soil pH, NH₄NO₃ had no lasting effect on soil pH, and CaSO₄ decreased the pH relative to that of untreated but cropped soils and its effect increased with time. Seedlings grown on CaCO₃-treated soil recovered about the same amount of additional N as seedlings grown on soil treated with 200 ppm NH₄NO₃. Yield increased with N supply and K uptake increased with N uptake. However, the application of K to a soil that provided little to plants did not cause a very great yield increase. Calcium sulfate increased yields only with the first crop on one soil and with the second crop on another soil. It was concluded that increasing the pH of the Ap horizon of Solonetz soils, as results from deep plowing, increases the availability of soil N to plants.